Phase 1b/2 study of combination <sup>177</sup>Lu girentuximab plus cabozantinib and nivolumab in treatment naïve patients with advanced clear cell RCC.
Authors: Elshad Hasanov, Lesley Flynt, Rebecca Slack Tidwell, Hyunsoo Hwang, Roserika Brooks, Lauren Michelle Wood, Travis Solley, Dahlia Mack, Yuko Yamamura, Aradhana M. Venkatesan, Eric Jonasch
Journal: Journal of Clinical Oncology (2023)

TPS4605 Background: Complete response (CR) is still a rare event in patients with advanced clear cell renal cell carcinoma (ccRCC). The combination of nivolumab plus cabozantinib was recently approved for the first-line treatment of ccRCC based on the CheckMate 9ER phase III study demonstrating improved progression-free survival (PFS) and objective response rate (ORR) in comparison to sunitinib. However, the CR rate was only 9%. Since the anti-tumor effects of immune checkpoint inhibitors are dependent on the presence of activated tumor-infiltrating T cells, drugs that could synergize with T cells’ anti-tumor activity can allow us to improve CR rates. Activation of the cGAS-STING pathway, the master regulator of anti-tumor immunity which is induced by radiation-induced DNA damage, is one promising mechanism that has been investigated. Many studies have shown that radiation treatment augments immune checkpoint inhibition. However, it is not always possible to radiate all metastatic lesions. Therefore, targeted peptide receptor radionuclide therapies (PRRT), have been developed by conjugating radioisotopes to receptor binding analogs targeting specific cancer cell surface proteins, thereby delivering targeted radiation to cancer cells in the body with minimal damage to surrounding healthy cells. 177 Lu girentuximab is the first antibody-radioisotope designed for ccRCC, targeting carbonic anhydrase IX-expressing cells, which includes &gt; 90% of ccRCC. It has been tested in metastatic ccRCC as a single agent and shown to be safe and effective in stabilizing disease in 57% of pts. In this study, we hypothesize that 177 Lu girentuximab-induced DNA damage will potentiate the STING pathway, and this activation will synergize with nivolumab and cabozantinib to promote trafficking and infiltration of activated T cells to tumors and achieve higher CR rates. Methods: Up to 100 patients with treatment naïve, biopsy-proven ccRCC with adequate organ/marrow function with ≥1 evaluable lesion by RECIST 1.1 will be enrolled. A 5-patient safety lead-in will evaluate myelosuppression. Ongoing safety, and futility monitoring will employ a Bayesian approach. The sample size was chosen for reasonable operating characteristics to distinguish a CR rate of 18% as better than 9% using a beta(0.09, 0.91) prior. Secondary endpoints are objective response, PFS by RECIST 1.1, and overall survival. 177 Lu-girentuximab 1480 MBq/m 2 (61% of single agent MTD) will be administered every 12 weeks for up to 3 treatment cycles. After the first cycle, nivolumab and cabozantinib will be added starting with the second cycle at standard dose. To explore the effects of the combination therapy on inducing activated T cell infiltration, patients will undergo pre/post-treatment PET scan with [18F]F-AraG radiotracer as well as biopsies for single cell, spatial transcriptomics and proteomics studies.